Method of and apparatus for making plastic tubing



Oct. 7, 1952 G. A. LYON 2,

METHOD OF AND APPARATUS FOR MAKING PLASTIC TUBING Filed Aug 15, 1949 2 SI-IEETS -SI-IEET 1 li y-2177b? I I 60K6 144554 7 [mm E; 7 fi s.

Oct. 7, 1952 QN 2,612,656

4 METHOD OF AND APPARATUS FOR MAKING PLASTIC TUBING Filed Aug. '13. 1949 I 2 SHEETSSHEET 2 4a H I 25 w 27 30 33 40 if Patented Oct. 7, 1952 UNITED STATES PATENT OFFICE METHOD OF APPARATUS FOR MAKING PLASTIC TUBING George Albert Lyon, Detroit, Mich. Application August 13, 1949,, Serial-1N0. 110,091 18 Claims. '(01. 18-14) The present invention relates to improvements in the manufacture of tubing from thermoplastic material and more-particularly concerns a method of and apparatus-tor the continuous production of such tubing. a

An important object of the present. invention is to provide anim-proved method of andapparatus for the continuous production of tubing from thermoplastic material, A

Another object of the invention is to provide an improved method of and apparatus for the continuous production of, tubular sections of predetermined length from thermoplastic material.

.A further object of the invention is to provide an-improved method of and apparatus for extruding tubing from thermoplastic material and resulting in tubing of improved accuracy of proportions. I

Still another object ofthe invention isv to pro,- vide improved means for producing tubing .from thermoplastic material and severed into'lengths having accurately sheared ends.

Yet .another object of the invention is to provide means for producing and'handling tubing made from thermoplastic material.

According to the general features of the present invention there is provided an improved method of making tubing from thermoplastic material, which comprises extruding material in thermoplastic state through a tube-forming die having a tube-forming passage oflsubstantial length, in the first portion of the tube-forming passage accommodating the material in thermoplastic condition, and in the final portion of the tube-forming passage cooling the formed. tubing to substantially set condition so that the tubing emerges from the forming die in shape-retaining form.

According to other general features of the invention there is provided a method of making tubing from thermoplastic material which comprises extruding material in thermoplastic condition through a fixed forming die, continuously cooling the forming die to set the thermoplastic material therein, extruding the set thermoplastic material from the die to substantial length, and severing the tubing into a section of tubing at the extrusion outlet of the nozzle.

7 According to yet other general features of the invention there is provided in plastic tubing forming apparatus, means for extruding material in thermoplastic form including an extrusion die having an elongated cylindrical extrusion passage, and means for cooling the discharge end portion of the extrusion die to substantially set the tubing prior to leaving the extrusion die.

According to other features oi'the invention means are provided at the exit of. the extrusion die for cleanly shearing the extruded. tubing. into sections.

According to yet other features of the invention means are provided for receiving. theshea-red sections of tubing and arranged. to convey the tubing sections away from. the extrusion point for further cooling.

Other objects, featuresand advantages. of. the present invention will be readily apparent from the following detailed. description of a preferred embodiment of the invention taken in conjunction with the accompanying drawingain which:

Figure 1 is an elevational view of aplastic tubing forming apparatus. embodying the features of the present invention;

Figure 2 is afragmentary horizontal sectional view taken substantiallyon the line III.-II of Figure 1;

Figure .3- is an enlarged vertical sectional detail. view takensu'bstantially on the line .IIL-III of Figure 1.;

Figure 4. is anenlarged vertical. sectional detail view through the extruding dieassembly and associated mechanism taken. substantially on. the line l'V-JV of Figure 1; and

Figure 5 isa horizontal sectional detail view taken substantially on. the line 'V--V of Figure 4.

As shown on the drawings:

Apparatus is provided for practicing the method which includes .p'lasticizing thermoplasticmaterial suclrior example, as ethyl cellulose, cellulose acetate, vinyl resins, etc. The thermoplastic material is worked and forced through a forming die having a tube-forming passage. As the formed thermoplastic material is .Iorced on through the die, it is cooled and substantially set while in continuous movement and' is then extruded in substantially set condition as a tube of substantially uniform wall dimensions. After a predetermined length of the formed tube has been extruded, it is cutoff cleanly at the point of extrusion to form a tubular section of given length.

Throughouta substantial portion of its final length, the forming and extrusion die is .liollow and cooling-water is sprayed thereinto for effecting the setting of the formed "tube therein and supported on the floor H by means such as;a-.

flange l3 and depending through an appropriate aperture It in the floor. Plastic material in 'gra'n ular form may be dumped into the hopper IZ-by way of a chute 15. From the hopper the granular thermoplastic material is Worked downwardly by a spiral screw ll into a hollow cylindrical plasticizing and working housing 18. Means for operating the screw I! may comprise a motor I9 and appropriate gearing supported by appropriate framework 2E above the hopper I2.

As best seen in Figure 4, the lasticizing' and working housing If; is provided with a hot water or steam jacket 2! by which the vertical working passage therein having a liner 22 is heated to the temperature at which plastic material 23 is rendered thermoplastic; As the material is plasticized'it is also worked to a smooth anduniform consistency by the screw l1 and forced downwardly *in the plasticizing and working a chamber.

From the lower end of the casing lfipthe thermoplastic material is forced-by the screw i! into and through a tube forming die assembly 24 supported by the lower end portion of the casing. This die assembly includes a spider member 25 which is accommodated within a recess '2'! in the lower end of the casing I3 and has a central core portionifi opposing the lower end of the working and plastic material driving screw ll. As the thermoplastic material 23 is forced through the spider 25' it is gradually shaped into the tubular form ultimately desired. For this purpose, the core 28 includes a tapered head 23 which deflects the plastic material outwardly to, a thinner section defined by the remainder of the core which may be gradually tapered to the ultimate inter nal diameter-oi the plastic tube but is preferably formed cylindrical'as shown at 30 throughout the major portion of its length and then'has a lower radially flaring terminal section 3| having as its maximum" diameter the ultimate internal diameter of the f nished plastic tubing. The outer wall of the spider encircling the core 28 is preferably formed onthe plastic tubing. t v I Since' for 'theattainme'nt of'uniform plastic pressure through the spider 2 5; it is'highly desirable to have the'core 2B concentric with the screw fi,.means'are provided for effecting accurate adjustment in assembly of the spider. To this end, the spider 25 is provided'with a lateral flange 32fa'ccoznmodatedwithin a counterbore 33, both the body of the spider and the flange 32 being accommodated loosely for transverse adjustment within the recess 2'! and counterbore' 33. A clamping plate ,3?! secured as by means of screws 35 to a lateral fiange..3'l. at the lower end of the casingj" l8, clamps the spider 25 axially into position. For this purpose. the clamping plate 34 has a centering boss'38 extending into the count' terbore 3 3 and bearing against the spider flange 32fto drive the upper end of the spider against a shoulder 39 at the upper end of the recess 27. By reason of the lateral clearance aiiorded about ultimateoutside diameter of the the spider 25, it is adapted to be adjusted for concentricity by means of a uniformly arranged series of set screws 40 threaded horizontally through the flange 37 into engagement with the edge of the spider flange 32.

Cooperating in plastic .tube forming relation with the lower end of the spider 25 are die means including an outer die tuba and an inner die :tube 42. The-outer die tube 4| eirte'rid's coaxially through and is carried by the clamping plate 34 and has the upper end portion thereof concentrically cooperating with the-terminal tapered portion 3i of the spider core. The inner die tube 42i s 'carried by an attachment plug 43 and is secured concentrically as by means of a screw 44 extending through the attachment plug to the 'lower end a of I the" spider core 28.

The inside diametenof the outer die tube 4| corresponds to the'ultimate or finished diameter of the plastic tube and the outside diameter of the inner forming or "diatribe '42 corresponds to the desired fine ished inside diamet'eiof the plastic tube. When the spider 25 is adjusted to concentricity with the screw I l, concentricity of the inner die formingtube 42 with the outer die forming'tube H is also attained' Thusjthe thermoplastic material 23 is forced smoothly and uniformly 'and with uniform pressure'into and through the tubular forming passage in the die assembly 24 provided by the spider and theconcentric die'forming tubes 4! and 42. 1 p I Notonly is thetube forming passage in the die assembly Zt long enough foraccurate, homo geneous tube wall formation; but also long enough to enable'substantial settingof the thermoplasti c material of'the formed tube, so that at the'point ofeXtrusion, the tube is solid enough to be self-sustaining as to form. To this end; the die tubes 4!- and A2 extend downwardly coextensively a distance which is; substantially-in excess of minimum tube-formingrequirements, in the present instance extending substantially beyond the lower face ofit heclamping plate 34 and thus afiording elongated relatively thin wall radiator surfaces which maybe exposed for cooling and which are preferably positively'coo'led'so as to set the plastic material of the tubing. Although the radiator section of 'the'formin'g tubes may be externally cooled by a cooling jacket through which a coolant fluid is circulated, a simple, efilcient expedient comprises directing coolant such as cold water in theform of jets or sprays45 against the outer cylindrical periphery of the outer radiator section providedby the outer tube 4!. One or morejin the present instancesh'own as..a pairof circular tubular spray'he'ads' or rings 47 having inwardly directed spray ports 48 and concentricallyencircling the outer tube at may be prothis purpose, the/interior of the inner radiator section provided by' the inner I die tube 42 is also subjected to positive cooling and conveniently affordsa cooling chamber 5! into which a plurality of jets or; sprays 52 of coolant fluid-such as water are directed. #Means for producingthe coolant sprays 52 efiicientlycomprise a pluraliy of appropriately dimensioned nozzles 53 which.

a spray head 54 dismay form integral parts of posed substantially concentrically below the chamber 5| and carried by a coolant supply tube I t will thus be evident that the extruded tubing: -51 is not only quite accurately formed as to wall thickness and concentricity in the-forming die assembly 24, but the substantial accuracy in these desirable dimensions and proportions are posi-- tively maintained in-the extruded tubing by reasonof the fact that the tubing is substantially set and self-sustaining as to form prior to extrusion. In order to reduce friction of the substantially set tubing in the lower portion of the tubing passage in the radiator section of the tubes 41' and 42, a suitable lubricant may be introduced into the plastic mix or a lubricant may be intro-' duced' into the 'radiator'portion'of the tube passageway in any preferred or known manner. However, it should be understood that by the use of coolant sprayscooling in the-radiator section of the tube forming die assembly occurs gradually so that there is no excessive or sudden chil1 ing ofthe plastic such as might cause crazing, cracking or distortion of the tube surface. The length of the radiator section is properly proportioned withrespect to the speed of operation and the thermoplastic temperature of the plastic material so that actual settingjof the plastic material of the formed; tubing occurs fairly close to the point of 'cxtrusionfrom the die assembly. This means that theplastic material of the tubing gradually cools and congeals: from the thermoplastic to the set condition thereof substantially throughout travel through the, radiator section but 'at the point of: exrusi'on and for some. indefinite short distance prior to the point of extrusion is set to the desired form. sustainin condition. This does not necessarily mean. that the material has attained full'hardness'or what may betermed the. fully curedpcondition at the point of extrusion but at this point the. material" will resist ordinary deforming factors and will still be in, a substantially warm or evenflholt condition below the temperature at which it wasthermoplastic. I I I Y I I To facilitate handling; the. finished plastic tubing '51- is out into sections of preferredlen'gth.

6 best seen in Figure 5, the knife shafts and spur gears 63 are equidistantly spaced around the supporting flange 59 and thespacing between knife assemblies is such that the shortest "practicable blades 60 may be used tocooperate "in overlapping strokes in operation, as indicated by the circular knife sweep indicating-dot-dash lines in Figure 5', for simultaneousseverance action upon actuating gear assembly.

the'fonmed and set plastic tube.

For periodically driving ring gear :64 as v desired to sever a section of plastic tubing 51, means are provided such as an electric motor 65 which may be carried by the lower section of the extruder casing l'8 (Figure 1) and drives a shaft 81 carrying a drive gear 68 meshing withthe ring gear 64. By preference a clutch assembly 59 is inter-posed between the shaft of the motor 65' and the drive shaft 61 and an oper'ating handle- "I0 is adapted to be manipulated to operate the clutch for selective actuation of the knife B-y preference the clutch 69 is a one revolution clutch which automatically throws out after each revolution.

Thus, when the clutch 69 is manipulated to actuate theknifegearing, the gearing is operated at high speed to rotate the knife shaft 63 in unison and substantially whip the knife blades '60 through their cutting sweeps and in which each of the blades. cooperating with the ends of the tubes 4| and 42 shears through a small arc of the plastic tube 51 at the point of extrusion, with each of the severance arcs overlapping at its ends with the adjacent severance arcs so that the-tube is cleanly and virtually instantaneously severed on a uniform horizontal, square plane. High speed in the cutting operation is-essential if the tube forming process is to be continuous, as is preferred. The desired high speed is attained-by the multiplicity of overlapping sweep, relatively short knife blades each simultaneously "cutting but a small arc of the formed tube in a cutting sweep or stroke that is faster than the rateof advancing movement of the newly formed tubing. Since the tubing is still hot and thus not fully hardened er brittle, although sufliciently set to be form sustaining; and the ends. of the tubes 4| and 42 cooperate substantiallyas shearingblocks the cutoff blades a clean, square-cut or shear of "the tube end isaccomplished.

By the present invention meansareprcvidedlifor sectioning the. tubing substantially as of the extruding dieassembly- 24- without pause in the continuous forming process. As amatteroffact, the, extrusion ends of the die tubes 41 mm 4?: are

utilihed as part of the tube severing mechanism.

of the die tube and preferably with the lower face of the flange 5'9" coplanar-with thecoterminus'l'ower ends of the tubes 14 i and 42.

Operati-velysupported by I the carrying flange '59--is a set of tube severance knife blades- 60.

Each of the blades 60 is carried by'a hub- 6! 'se- 1 cured to a vertical shaft 6-2 appropriately journaled' in the flange 59 and carryingon its upper end above the flange 59 a spur gear 63 forming part of a "gear assembly including a ring gear 64 drivinglymeshing with the spur gears 63. As

forming process; Th'at.is, the tubingt'is' cutlnto sections at the extrusion'end of'the formingand wane the plastic tubing 51 is being extruded from the die assembly 2'4, spent coolant fron fthe coolant streams 45 maybe directed against the exterior-0 1" the tubing through drairr'hciles l'lpfin the knifesupporting-1 flange 59 (Figure 5'l for additional cooling of the tubing. In. addition, spent coolant from the coolant streams 52 may run down the interiorof the formed tubing; and assist in continued cooling of the tubing. As each section of tubing 51' is severed, it desirable to convey the sameaway from the extru der in an upright position for drainage of' coolarnt thereream and for further cooling before stockpilin or otherdisposition of the tube sections. this purpose, means are provided: by the pres en t inventioncomprising a conveyor preferably in the form of a tum-table 12- onto which each of the tube sections 51 will drop'endwise. pon severance and beconveyed in an upright position away from the extruder-. Convenientgmeansfcr retaining'the-plastic tube sections againsttippi'ng onof the turntable l2 comp-rises a series of the coolant supply pipestandards 55- which for tl is purpose are mounted at suitable ir-itervalsabout the periphery of the turntable I-2 andwith' the turntable solccated that each of the dual purrpose pipe standards. "55 can -beabrought successively iinto substantially concentric registration below: the extruder; The height ofw each of. the pipe. standards 55 andimore specially the overall height thereof including-"the; tri-nozzle spray head 54 thereon is suchthatasuificient clearance .-is afiorded below theextrudin end-of the {extruder--die assembly,.,2 l to enable movementof a severed tube section away and registrations-cf a succeeding one of the pipe standardsunderthe extruder before the advancingend of .a succeeding pcrtioncf the plastic tube being formed drops below the elevation of the top .of the standard to be-received therein. After the, tube has descended to sufiicient length about the associated standard the tube section is, severed just before the lower end reaches the turntable-Hand drops "down by gravity clear of the continuing-advancing end of the next succeeding section, the turn.-

table 12 being-promptly turned incremently to bring the next succeedin pipe standard into tube reofii position. 5 r ;Means for turning the turntable l2 mayzcomprise anelectric motor-2'13 supported belo-wthe turntable 72 on a turntable carryingpedestali i, appropriate neans such as belt'and pulley drive 15 being provided for turning of the turntable by the motor 13.. Of course, suitable means such as synchronous electrical controlor mechanical Coolantfiuid isconducted from a suitable source by vvay .olifa conduit 8|} into, the pedestal l4 and passes up, through a boreBI in the boss 19 and a'l'aterafl outlet port-ortpassage- 82 into eachuof the delivery ducts-ll as the latter is brought into registration with the outlet port 62 by rotation of the turntable l2 and as the respective supply pipe standard ,-55 ,thus brought into registration assumes operative position beneath the extruder.

, QWl iiIe a mere movement of the delivery ducts TLinto, andcutof registration with the supply port 82 may. be relied .upon to turn: on and shut on" the coolant fronrthe respectivecoolantsupply standards, positive valve controlmeans may be supplied for thespurpose .One convenient form of such control valve comprises a valvaassembly 83 (Figures land 3) interposed in the coolant source duct 89 and appropriatelyplaced so that as each of thelcoolant supply pipes 55 comes into registration with the extruder -a-pi'v oted lever 84 is pressed down bythe delivery pipe 11 f such coolant supply pipe todepress a valve opening button-B5 In the intervals while. the turntable is inn otion to transport, a finished tube section away from the extruder and a succeeding coolant supply andtubing retaining pipe standardis being moved into position,- the valve controlling button 85 automatically pops up to thedasl line position shown in: Efigure 3 andthus .cutsfoffjthe, coolant supply until the succeeding coolant delivery duct 11 depresses the control lever 84 and the control duct 85.; I 1 7 From the foregoing it will be apparent that the present invention dennesa novel continuous .trusiondie.

8 plastic tube forming process and a-pparatusand cyclically operable means for severing the formed plastic, tubingi'into sections or lengths, as well as other cyclically 1 operable means for conveying the formed, sections away from the extrusion point. It will alsobeapparent that the process and apparatus are well suited ,ror manufacturing plastic tubing in a largevariety of sizes either as to diameter or length, l w i "I claim asmy inventionzj 1. In a method ;of making tubing from thermoplastic material, driving thermoplastic material into a -tube-forming die, directing streams of coolant against the die, cooling the die to set the die in set tubular form.

the material, and extruding the material from 2.' In a method-of makingplastic tubing, forcing thermoplastic material into: an elongated tubular tube-forming die passag way, directing streams of coolant against the interior and the exterior; surfaces of the die, gradually cooling the formed material in said'passageway, and extruding the formed material inset condition from the passageway.

,3. ,In the manufactureof plastic tubing, drive ing thermoplastic material into and. through-a downwardly directed forming. die. having an elongated tube formin passage, internally-and externally cooling the forming die .by directing streams of liquid coolant thereagainst to cool ,and setuthe thermoplastic material in the die passage, extrudingthe set material in tubular form from said diepassage and continuing the cooling of the plastic tubing by running the spent coolingliquid downwardly thereover. Y j

In plastic tubing ,lforminglapparatus, means for extruding material, in thermoplastic-form including an extrusion die having an 7 elongated cylindrical extrusion passage, and means ifo'r directing streams of coolant against the die for cooling'ithedischargeend'portion of metamsio'n die to substantially set thetubing prior to leaving'the' extrusion diei T 5L In .plastiO tubing formingapparatus, means for extruding" material 'inl therrnoplastic form including a hollow extrusiondie having an elongated cylindricalfextrusionjpassage, means for 'direqti lgwstreamsf of lcoolant against the interior of the hollow extrusion die" for cooling the discharge end portion of--.the..extrusion die tosubstantiall'y. set the tubinglprior to leaving the ex,-

'6. jin plastic tubing :6 r ining I apparatus, means for extruding-material n tliermoplastic form including ahollo v' extrusionjdie having anelom gatedfcylindrical, extrusion passage, v means for directing. streams of coolant against the interior and exterior. of the elongated extrusion'die for cooling the discharge. end portion of the extrusion die to substantially set the tubing prior to leaving the extrusion clie, means at the exit of theextrusion diefor cleanly shearing the extruded tubingintosections, andmeans for re:-

ceiving the sheared? sections of tubing andarranged to convey theltubing sections away from the extrusion point for furthercooling.

7. In combination in a plastictubingextruder, means including a thermoplastic material plasticizinglfchamber having a drive screw operating therein an extrusion die receiving the thermoplastic material from said chamber as impelled by said scre w, said die having an elongated tube-forming passage, said passage includinga radiator section andan extrusion orifice, and means: for positively cooling said radiatorsection to the setting temperature of .theplastic material so that the material will'bej extruded in substantially; set condition, said cooling means comprising a coolant, spray radiatorsectiom 8. In combination in a plastic tubing extruder, meansincluding a thermoplastic material-plas ticizing chamber j having adrive. Screw operating therein, an extrusion-,die receivingthe thermo plastic-material from" said chamber as impelled. by: said screw, said die, having an elongated tubeforming passage, said passage includinga radiator section and an extrusion orifice, and means for positively cooling said radiator section to the setting temperature of the plastic material so, that thematerial will be extruded in substantially set condition, said cooling meanscomprising a spray head projecting sprays of coolant internally of's'aid radiatorsi'ection. r

9. In combination in a plastic tubing extruder, means 1 including a thermoplastic material .pl'asticizing'chamber having-:ajdrive screw operating therein, an, extrusiong-die receiving the, thermoplastic -material from said chamber as impelled by said screw, said di'ehaving; an elongated tubeforming passage, saidupassage,includinga radiator section and extrusionorifice, and means for positively cooling said radiator section'tothe setting temperature of the plastic material so that the material will be extruded in substanu tially set condition, said radiator section being internally hollow, and said cooling means comprising an encircling spray ring and an'internal spray head for directing coolant fluid against the radiator section both internally and externally.

ringencircling said 10. In combinationin a plastic tubing extruder, a cylindrical thermoplasticizing chamber, means operating in said chamber for mixing and driving thermoplastic material toward a discharge outlet, a forming spider mounted at said outlet and having a plastic tube forming preliminary passageway of progressively diminishing wall thickness therethrough, said spider including a downwardly openin hollow core portion projecting therebeyond, a forming die member encircling said projecting core portion, means supporting said encircling die member fixedly, and means for directing coolant spray into said hollow core portion.

11. In combination in a plastic tubing extruder, a pair of cylindrical telescoped members of differential diameterproviding opposing tube wall forming die surfaces, said members being coterminus and defining a tube extrusion port, and cut-off means carried by the outer of said members and comprising a series of synchronously operable cut-off knives coordinated to intersect predeterminedoverlapping arcs of an extruded plastic tube wall, the coterminus extrusion port ends of said members cooperating as stationary shear elements across both of which said knives sweep in shearing relation to sever a length of extruded tubing.

12. In combination in a thermoplastic. tube forming apparatus, a downwardly directed plastic tube extruder including an, internally hollow downwardly opening extrusion die, an upwardly projecting coolant supply pipe standard hav-. ing a spray head at the upper end thereof located in spaced relation below said die and arranged to discharge coolant spray into said hollow die member, and means for severing a section of extruded tubing to drop downwardly about said standard.

13. In combination in a plastic tube forming apparatus,,a downwardly-directedplastic. tube ard and carrying a, succession, of; similar coolant supply standards, for successive, registration with said tube-forming die to-receive a formed plastic tube sectionsa;

. 14. ;In combination in a:plastic",tube forming apparatus, a downwardly, directed plastic tube extruder including an internally-hollow down.-. wardly opening extrusion die, an upwardly projecting coolant; supply; pipewstandard; having ;.a'

spray head at the. upper end thereof 1O0&t8d;1iY-1 spaced relation belowwfsaid: die-and arranged-11:0 discharge, coolant :spray; into said, hollowndie member, meansfor. severing a sectiontof. extruded tubing to-drop downwardly about-said standard, a;turntable supporting saidfstandard and'i'carrye inga successionof similarrcoolant supplystande ards for successive registration. with: said .tube. forming die to receive a succession of formed plastic tube sections, and means for controlling the supply of coolant to each of the coolant supply standards for discharge therefrom only when in registration with said plastic tube forming die.

15. In combination in a plastic tubing extruder, a pair of cylindrical telescoped members of difierential diameter providing opposing tube wall forming die surfaces, said members being coterminus and defining a tube extrusion port, and cut-off means comprising a carrying flange mounted on the outer of said members and supporting a plurality of equally spaced knife blades coordinated in rotary operative cut-ofi cooperation to intersect predetermined overlapping arcs of a plastic tube wall extruded from between said members, the coterminus extrusion port ends of said members cooperating as stationary shear elements with said'knife blades, said knife blades each having a shaft carrying a spur gear and ring gear of larger diameter than said outer member meshing drivingly with said spur gears to effect simultaneous rotation of the knife blades, said knife blades coacting with each other e and with both of said ends of said members simultaneously to sever the plastic tube wall uniformly throughout its circumference.

16. In apparatuswherein tubing is formed from plastic material by downward extrusion into sections of substantial length in self-sus-' taining condition, a conveyor structure including a movable member controlled to move progres:

sively under a tubing extruder to receive on suc cessive portions thereof upstanding respective lengths of the tubing, means for driving said conveyor member, and respective upstanding standards at each of said conveyor portions down over which'each of the tubing sections as formed is adapted to descend until the lower end of each of the tubing sections engages the conveyor member with one of the standards extending up inside of the tubing section to support the tubing section against tipping off of the conveyor mem ber until the tubing sections have been conveyed away from the extruder for removal from the conveyor.

17. In apparatus of the character described, wherein plastic tubing is extruded from a nozzle,

succession .of

11'. a cutter mechanism comprising a radially-outwardly extending annular supporting- 'flange structure arranged to'be suppofited externally of the nozzle adjacent toi'the extrusion end of the nozzle, a plurality of elongated butter knives, each of said knives being s'upporteel -adjacent to one end by'a shaft rotatably su ported lay-said flange structure ior swing ingof the knivesin intersecting arcs with respect to each othef'afid to the'extru'sion end :of the nozzle forsevering extruded tubing inte' sections upon extrusion from the nozzle, each of said shafts having a spur gear thereon, and aring gear meshing-with said spur gears for rotating the spur gears simulterseeting --arcs with respect poaen other and to the extrusion end of the nozzle for sevez' ing extruded tubing into sections qup'on extrusion from the muzzle; each Of Said-Shafts having a spur gear thereon, and a ring gear meshing-with said spur gears for rotating the s'pua gean s simultaneously for synchronous operation of :the knives and having meansfor di ivin-g engagement by drivingme'ans, said flange structure having a seriesvof openings therethrough ferdpai-nage of coolant running downthe nozzleon'to the-flange structure.v

-- GEORGEALBERTLYQN The following references are 'o f i'ecord in'the file of this patent:

UNI TED STATES PATEfiTS I Date 20 Numbe'n 272,727 Ly1e' Feb. 20, 1883 515,564 1 Weissenborn- Feb. 27, 1894 1,603,325 Davidson et al. Oct. 19 I926 1,814,819 Boswell July 14 I931 25 2,384,521 Andersen emu Sept.- 11,1945

-Wallade;g s saea s May 7., 1946 

